1. Field of the Invention
The present invention relates to optical fibers and, more particularly, to a device for coating optical fibers.
2. Description of the Prior Art
Known devices for coating optical fibers typically comprise a housing that contains a lengthwise bore, and a nozzle holder which contains a receiving aperture located in this lengthwise bore. An inlet nozzle with a first nozzle bore and an outlet nozzle with a second nozzle bore, through which the optical fiber can pass, are arranged at a distance from one another in the receiving aperture of the nozzle holder. A space for applying a coating material to the optical fiber is formed between the inlet nozzle and the outlet nozzle.
Such a device for coating optical fibers is used for example to manufacture a glass fiber for the transmission of optical signals. As is known in the art, an optical fiber may be manufactured by drawing it from a glass preform. During manufacture, the glass fiber is guided over deflection pulleys, which makes it necessary to coat the fiber to protect it against damage. To that end, one or more layers or coatings, for example of a polymer material, are applied to the glass fiber cladding. Typically, these layers have different mechanical properties when several layers are applied.
In known devices for coating an optical fiber, both the inlet nozzle and the outlet nozzle are located in the receiving aperture of the nozzle holder and are affixed to the receiving aperture by sealing rings, which seal the nozzles in the radial direction. The sealing rings are located in a groove formed around the inlet nozzle or the outlet nozzle, for example. The nozzle holder is also affixed in the lengthwise bore of the housing with sealing rings that operate in the radial direction. Seals formed in this manner between two adjacent components require a radial space between the two components, namely the inlet nozzle or the outlet nozzle with respect to the receiving aperture, and the nozzle holder with respect to the lengthwise bore of the housing, which measures about 0.01 mm.
A radial space between components that are sealed against each other in the radial direction has the disadvantage of poor reproducibility during assembly of the device, e.g., after replacing the nozzles, and every new assembly of the components in the device. This poor reproducibility results from the tolerances associated with the required radial space exceeding the permissible production tolerances of the inlet and outlet nozzles, and thereby the coating of the optical fiber, by several magnitudes. Therefore, the uniform application of a coating of a defined thickness is not always guaranteed with such a known device for coating an optical fiber.